Adherence of one bacterial cell type to another has been proposed as an important mechanism for dental plaque formation. One form of interbacterial adherence, intergeneric coaggregation, has been studied extensively and is remarkable in its specificity and its ubiquity among oral bacteria. Veillonella, Prevotella, Actinomyces and Streptococcus utilize similar mechanisms to adhere to common streptococcal coaggregation partners. A proteinaceous adhesin on each of these genetically diverse cell types recognizes a carbohydrate receptor on the streptococcal partner. These interactions are all inhibited by lactose, N-acetylgalactosamine and other related galactosides. Moreover, mutant streptococci which lack the receptor for one of these adhesins fail to coaggregate with each of these cell types. We hypothesize that if each of these organisms recognizes a common streptococcal receptor then purified veillonella adhesin will block each organisms' adherence to these streptococcal cells. Veillonella and Streptococcus are both found in high numbers in dental plaque, exhibit a nutritional relationship and have been demonstrated by in vivo studies to have specific surface interactions which play a role in veillonella colonization. They are an exceptional example of the intergeneric interactions which characterize the microbial ecology of subgingival dental plaque. the aim of this proposal is to confirm the role of a 45 kD protein from V. atypica PK1910 in mediating this class of interactions with oral streptococci and demonstrate its ability to block these diverse interbacterial interactions. First, monoclonal antibodies to V. atypica PK1910 will be isolated which block these interactions and will confirm the role of this protein in adherence. Simultaneously, the genes which encode this adhesin will be isolated, cloned and sequenced. This genetic approach will also confirm the role of this molecule in adherence, enable us to compare its primary structure to other known bacterial adhesins and introduce it into the more easily manipulated genetic background of E. coli. The monoclonal antibodies will then be used to purify the adhesin from either the wild type cell or from recombinant E. coli which express the protein. finally, the purified adhesin will be tested for its ability to block the adherence of Veillonella, Prevotella, Actinomyces and other Streptococcus to these oral streptococci. This purified adhesin which blocks multiple oral bacterial interactions will serve as a prototype for a new class of oral hygiene agents which function in inhibiting or modulating cell-cell surface interactions in dental plaque. Moreover, these studies will provide the molecular tools for future structure-functions studies of the adhesin and studies to directly demonstrate the role these interactions play in oral bacterial colonization.